Partial knee replacement surgery (also called unicompartmental knee arthroplasty) is known in the art for the treatment of osteoarthritis of the knee joint. During partial knee replacement surgery, the bone and cartilage on the end of the femur and top of the tibia are removed. A knee replacement implant made of various biocompatible materials such as metal or plastic is then placed to function as a new knee joint. Depending on the condition of the cartilage on the undersurface of the kneecap, the cartilage may also be replaced. The knee replacement implant typically comprises (i) a femoral component which fits on the femur, (ii) a tibial component which fits on the tibia, and optionally (iii) a patellar component, made of plastic and which replaces the cartilage on the undersurface of the kneecap, and optionally (iv) a plastic insert which fits between the femoral and tibial components.
Placement of the knee replacement implant typically involves the steps of: (i) forming a tibial socket in the tibial plateau; (ii) performing at least one cut on the femoral condyle; and (iii) placing implants or components into the socket on the tibial plateau and into the cut in the femur. These steps are performed using precise instruments to create exact surfaces to accommodate the implant. For example, instrumentation and apparatus for arthroscopic unicompartmental knee surgery (which include a femoral component and a tibial component) are described for example in U.S. Patent Application Publication No. 2008/0275512, the disclosure of which is incorporated by reference. U.S. Patent Application Publication No. 2008/0039852 (the disclosure of which is also incorporated by reference) describes the use of a dual-sided cutter for forming the femoral trough and tibial socket by retrograde drilling.